Micro computed tomography analysis of the shaping ability of nickel-titanium instruments activated by continuous rotation or adaptive motion

Aim: The aim of this study; is to compare the shaping abilities of curved root canals with the μCT imaging technique using the TruNatomy, VDW.Rotate and Twisted File Adaptive file systems in two different motion kinematics. Material and method: In this study, 30 mandibular molars with fully formed apices and 2 separate mesial canals and 20°-40° curvature were selected. Access cavities were prepared and working lengths were determined. After the samples were scanned with μCT, 60 mesial canals were randomly divided into 6 groups (n=10). Group 1: TRN-CR, Group 2: TRN-AM, Group 3: VR-CR, Group 4: VR-AM, Group 5: TFA-AM, and Group 6: TFA-CR shaped with kinematics. A second μCT scan was performed using the same parameters as the first scan. Dentin volume, transportation, and centering ratio were evaluated at 3, 6, and 9 mm levels on μCT images before and after shaping. Results: The TRN groups showed statistically significantly lower volume differences than the other groups in both kinematics (P < 0.05). The VR-CR and TFA-AM groups showed a statistically significantly higher volume difference than the other groups except for the VR-AM group (P < 0.05). There was no statistically significant difference between the groups in the amount of transportation and the centering rate at any level (P > 0.05). Conclusion: TRN groups removed less dentine in both kinematics. The TFA system removed more dentine when used with adaptive kinematics compared to continuous rotation kinematics. Centering rate and amount of transport were similar between groups at all levels; under the conditions of the current study, all three systems can be used in adaptive motion and continuous rotation motion. Keywords: Adaptive motion, continuous rotation, micro-computed tomography, shaping ability, TruNatomy, Twisted File Adaptive, VDW.Rotate